#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    bool isInterleave(string s1, string s2, string s3) {
        int m = s1.size(), n = s2.size();
        vector<vector<bool>> dp(m + 1, vector<bool>(n + 1));
        if (m + n != s3.size())
            return false;
        dp[0][0] = true;
        s1 = " " + s1, s2 = " " + s2, s3 = " " + s3;
        for (int j = 1; j <= n; j++) {
            if (s2[j] == s3[j])
                dp[0][j] = true;
            else
                break;
        }
        for (int i = 1; i <= m; i++) {
            if (s1[i] == s3[i])
                dp[i][0] = true;
            else
                break;
        }
        for (int i = 1; i <= m; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                if (s1[i] == s3[i + j]) dp[i][j] = dp[i - 1][j];
                if (dp[i][j] == false && s2[j] == s3[j + i]) dp[i][j] = dp[i][j - 1];
            }
        }
        return dp[m][n];
    }
};